This invention relates generally to hand trucks and more particularly to a two-wheeled hand truck with integral universal clamping system for securing a load to the hand truck.
Conventional upright two wheeled hand trucks of various designs are well known and have been in use in and around warehouse spaces and cargo docks for many years. They are generally of simple metal construction consisting of an upright frame extending vertically from a load bearing platform or toe plate, a handle area at the top of the upright frame and a set of wheels located near the bottom of the upright frame located on either side of the toe plate. Although hand trucks in their basic simple form are reasonably functional, a universal and common problem involving the use of this type of load transporting device has been the actual loading of cargo onto the hand truck and restraining or securing to the hand truck the many shapes and sizes of loads they are required to accommodate in normal operation. The general procedure for loading a hand truck requires the operator to slide a toe plate located at the base of the upright frame under the load to be moved, then hold the cargo back against the upright frame of the hand truck with one hand while tilting or pivoting the frame back locating the load directly over the wheels into the balanced position necessary for easy transport. It is often necessary when a particular load is too great in one or more dimensions to secure the help of another person to provide back pressure necessary for holding the load back in place against the upright frame and on the toe plate of the hand truck while the operator pivots or tilts the load back over the wheels into the balanced position for transport. It is also necessary in most cases for the operator to hold or stabilize the load with one hand to insure that the load remains in place on the hand truck while simultaneously keeping the load balanced over the wheels while pushing and steering the hand truck to it""s destination with the other hand
In an effort to better contain loads and simplify the overall handling and operation of hand trucks, a number of solutions to the loading and load restraining problem have been introduced ranging from the addition of specialized clamping or strapping mechanisms to complete and radical reconfiguration of hand truck geometry. The result has been the development of a multitude of different types of specialized hand trucks designed specifically to contain or handle a particular shape or geometric configuration of load such as filing cabinets, gas bottles, barrels and drums, luggage etc. Although these modifications have provided solutions to specific problems, they often times take away from the hand trucks ability to be used as a general-purpose device.
An example of a specialized configuration of hand truck would be Turek and Schobergs U.S. Pat. No. 4,893,824 wherein a hand truck for file cabinets is shown. Although the invention is equipped with a restraining device for containing a file cabinet, it is limited to use on loads that are roughly of the same square or rectangular configuration and size as a file cabinet if the restraining device is to be used. A load or cargo with considerably less depth than that of a file cabinet that is held in place with this retaining arm and clamping mechanism would require the unused or excess length of the retaining arm be extended back through the upright frame area where the operator is standing creating an obstruction for the operator and resulting in difficult manipulation of the hand truck Additionally, the upright frame consists of an upper frame and a lower frame that are telescopingly mated with the retaining arm extending from the upper frame section. The result of this design characteristic is that the retaining arm will only be functional over the upper half of the hand truck making it difficult to restrain flatter shaped loads or cargo with less height than a single drawer file cabinet.
Mr. Morissette""s U.S. Pat. No. 4,257,729, Hand Truck, is another example of the more specialized approach; arranged with a system for clamping the bead rim of a barrel or drum thus restraining it to the hand truck. The mechanism outlined in this patent for restraining the load would be of little use for loads that did not have a bead rim or were not a similar cylindrical geometric configuration as a barrel or drum.
The xe2x80x9cClamping device for use on hand truckxe2x80x9d outlined under Mr. Dunnings U.S. Pat. No. 4,492,505 is a load-clamping device added to or mounted on the upright frame sections of a hand truck. This approach is quite satisfactory for a number of load shapes and sizes, It is however somewhat more complicated to use in that the operator is required to select and mount a specific extension bar into an extension housing for restraining a particular type of load. The extension bar required would be dependant upon the type or shape of the load to be secured to the hand truck. It is important to note that the device of this invention secures the load to the hand truck with downward force compressing the load between the clamping mechanism and the toe plate of the hand truck. Although this downward force seems to be suitable for restraining certain geometric shapes of cargo for transport, In most cases it lends little support in the actual loading process as a back force which presses the load back against the upright frame of the hand truck is usually required to keep the load on the toe plate and in place against the upright frame of the hand truck when the upright frame is tilted or pivoted back over the wheels to balance the load for transport. In cases where the load extends outwardly from the upright frame of the hand truck any appreciable distance beyond the support of the toe plate, considerable downward clamping pressure would be required to hold the load securely between the clamp and toe plate to insure that the load remains against the upright frames when the hand truck is tilted back to locate the load over the wheels. As mentioned earlier, this particular step in the loading process generally requires that the load receive a backwards pressure holding the load against the upright frame of the hand truck. Excessive downward pressure as would be required to keep the load in place would further complicate the loading process if the cargo container is not substantially rigid on all surfaces such as a common square or rectangular cardboard shipping box, or if the load container has insufficient inside reinforcement In this case it may not be possible to apply the necessary downward pressure required to keep the load back against the upright frame without collapsing the container at the point where the clamping pressure actually contacts the load.
These are but a few of the examples that demonstrate the need for a hand truck that is truly universal, in that it will accommodate and restrain cylindrical and irregular shaped cargo as well as rectangular shapes over the entire height of the hand truck frame, is easily loaded by one person, has the capability to provide the load holding or restraining forces back against the entire length of the upright frame where it does the most good and can still be used in a conventional manner if clamping or load restraint is not necessary.
The present invention offers forth a universal hand truck with an integral clamping system designed to overcome the problems outlined above; comprising an upright frame section formed by two parallel tubular sections joined on the top end to form a handle, a toe plate which joins the upright frame sections at the bottom and extends forward or outward from the base of the upright frame providing for a load bearing surface. A pair of wheels mounted one on either end of the toe plate in such a way as to allow the upright frame to be pivoted or tilted back to locate the load over the wheels or free stand when not in use, supported by the two wheels and the toe plate. A plurality of horizontal metal straps are provided as cross ties extending between the two upright tubular sections adding strength and rigidity to the upright frame of the hand truck. Cross ties are formed in a slight concave arc to provide clearance for a vertical slide track and substantially fixed horizontally between the toe plate and handle of the two upright tubular sections that form the upright frame with approximate equal spacing.
A vertical slide track for carrying a sliding piston or slide lug and the load-clamping device is fixedly attached to each of the cross ties at a point equal distance between and parallel to the parallel tubular sections that form the upright frame. The vertical slide track is fixedly attached to the top of the toe plate and extends to the uppermost cross tie located a short distance below the frame handle at the top of the hand truck. A front portion of the tubular wall section of the vertical slide track is cut away over the entire length of the vertical slide track to allow for clearance of a coaxial clamping bar and clamping device which pivotally attaches the slide lug to the coaxial clamping bar allowing the load clamping device to be slid from the toe plate to the top of the vertical slide track providing for the ability to clamp or restrain a load over the entire vertical capacity of the upright frame of the hand truck.
A load clamping device designed to provide for load restraint by applying a clamping force back against the upright frame portion of the hand truck is capable of securing cylindrical, rectangular or irregular shaped loads that fit within an envelope defined by the height of the hand truck and the length of a coaxial bar clamping device. The clamping device consists of a telescoping coaxial clamping bar and a clamp body provided for with load retaining fingers. The coaxial bar which the clamp body is fitted to consists of a plurality of sections, one fitting inside the other and allows for telescopically extending the bar of the clamping device without overhang or obstruction created by an unused portion of a clamping bar when containers or loads that have minimal depth are secured to the hand truck. The clamping body is arranged to slide over the outside tube of the coaxial bar and is equipped with a means for rapidly locating and locking the clamping body to any point along the length of the outside tube of the coaxial bar. The clamping body has dual flex mounted clamping fingers located on either side of the clamping body and extending downward and arranged to restrain flat, cylindrical and irregular shaped containers or loads. Clamping fingers are engaged providing the necessary back directed force for securing or restraining the load by a simple operator activated handle conveniently located on the top of the clamping body.
When not in use, the telescoping coaxial clamp bar is collapsed, the clamping body is slid to a stop at the outermost end of the outside tube of the coaxial clamping bar, The clamping device is pivoted to a vertical position on the slide lug and the slide lug and clamping device is slid down into a vertical slide track to a stored position freeing the hand truck for conventional uses that do not require clamping or restraint of the load.
It is the object of this invention to provide a hand truck with an integral load-restraining device. It is also an object of this invention to provide a load-restraining device that can accommodate both cylindrical and rectangular shaped cargo. It is a further objective of this invention to restrain the load by applying a backward force. It is still a further objective to provide a clamping device that collapsible and can be retained inside the hand truck when not in use The foregoing objects including other advantages of the present invention will become obvious to those skilled in the art to which the invention pertains upon review of the following detailed description and drawings in which,